Zohran Mamdani needed supporters, numbers, live bodies.

His bid for student vice president at the elite Bronx High School of Science would ultimately crater, with its wayward pledge of fresh juice for all, squeezed from locally sourced fruits. ("I promised things that were simply impossible," he conceded years later.)

But through a blitz of frantic campus recruitment, inveterate bluffing and cajoling internet posts, a campaign much dearer to a teenage Mr. Mamdani -- and much more resonant to him now -- was hurtling ahead.

Cricket had never been recognized as an official sport in New York City's public schools. Mr. Mamdani, like many South Asian schoolmates who had grown up around the game, wanted in anyway.

And so, he and a friend effectively created a team themselves, with all the logistical fortitude available to distractible adolescents, amassing a cache of bats, pads and player sign-ups ("brown ain't no requirement to play this game," Mr. Mamdani urged on Facebook) and working to persuade enough students and adults that they were fronting a legitimate operation.

"He was sort of campaigning," Avneet Singh, an eventual teammate, said in an interview. "I saw Zohran on campus running around with this group of kids saying, 'We're going to be the cricket team.' So before it was even a team, I think he had to pretend that it was a team."

For most politicians -- for most people -- high school is a formative time. Awkwardness is overcome (or not). Mistakes are made (and repeated). Personas congeal into personalities.

For Mr. Mamdani -- for most people who went to his very particular high school -- it is something closer to a skeleton key.

Fifteen years after his graduation in 2010, the creation of the cricket team still earns prominent mention on his State Assembly biography page, reflecting both the limited legislative record of a 34-year-old lawmaker and the early education of a relentless grass-roots campaigner who is now the favorite to become New York City's next mayor.

By Mr. Mamdani's junior year, New York's public school system had added cricket to its roster of sports. After months of meetings with Bronx Science staff to codify their status, Mr. Mamdani and his team could make their city-sanctioned debut.

"It was one of the moments that taught me the power of organizing," Mr. Mamdani said in an interview, "and how to change your reality."

Despite Mr. Mamdani's professed early-onset cosmopolitanism as the Uganda-born son of India-born intellectuals, the New York of his earlier upbringing could be remarkably small, a reel of Upper West Side greenswards and bagel runs among mostly white friends who rarely ventured south of Lincoln Center.

It was at Bronx Science that the city first revealed itself to Mr. Mamdani in earnest, in all its brilliant and maddening imperfection, and where Mr. Mamdani evolved in kind, forming the sketches of the New York he aspired to see.

It was where he flashed high talent for the kind of dexterous social toggling that would serve him professionally; where he first commingled en masse with residents of considerably lesser means; where he negotiated (and ultimately embraced) a bespoke personal identity, with all the introspection and blunt-force brevity of a teenager feeling things out.

"Ugindia's Finest," read a flat-brimmed, custom-made hat that he sometimes wore at school.

"What Can Brown Do For You?" read a campaign slogan for Mr. Mamdani's ill-fated student government run.

While Bronx Science could feel like a haven for students who looked like him, Mr. Mamdani came of age at an institution that was and remains, by his account, an emblem of systemic school segregation.

Bronx Science is among eight specialized high schools where a standardized test is the sole admissions criterion. Amid yawning racial gaps in admissions, the exam has come under consistent criticism from lawmakers and activists for creating student bodies that fail to reflect the city's demographics -- an issue that has surfaced in Mr. Mamdani's mayoral campaign.

For years, Mr. Mamdani called for the abolition of the test, saying he had "personally witnessed just how segregated New York City public schools are" as a student. But in a signal of his pliability ahead of the November election, he has recently backtracked, saying the issue was a "struggle" for him.

For generations of students, the tailored circumstances at Bronx Science -- the test, the hyper-competitiveness, the other city-verified wunderkinds in the room -- have served as a bonding agent, keeping graduates tethered to the school and to one another with adhesive force.

Many recall their time there as an almost utopian experience of public education, in which students from all backgrounds and income strata converged to learn with and from one another.

"It was where I discovered who I wanted to be," the cosmetics heir Ronald Lauder, a 1961 graduate who has helped bankroll a super PAC boosting Andrew M. Cuomo's rival mayoral bid, said in a statement.

"Best years of my life," John C. Liu, a state senator who has vocally backed Mr. Mamdani, said recently before attending his own 40th reunion.

For Mr. Mamdani, Bronx Science is at once more complicated and far more recent history.

Bronx Science: "We're Worth the Trip"

The first thing to know about Bronx Science is that it is not easily impressed.

Notable alumni include the crooner Bobby Darin, the astrophysicist Neil deGrasse Tyson and the recipients of many shelves' worth of Pulitzers and Nobels.

Eleanor Coufos, the president of the Bronx Science Foundation, the school's alumni organization, recalled a celebratory luncheon for a recent Nobel winner. A friend of his could not make it and asked that a message be read in his absence.

"The card was like, 'You may have won the Nobel Prize,'" Ms. Coufos said, "'but I'll still be valedictorian.'"

The second thing to know about Bronx Science is that its loyalists can still have a large chip on their shoulder.

Another specialized school, Stuyvesant High School in Manhattan, is considered slightly more elite, creating a kind of perpetual little-sibling rivalry that only one side seems to recognize.

"We have quite a few elected officials," Kenny Burgos, a former New York state assemblyman who overlapped with Mr. Mamdani at Bronx Science, said pointedly of his school's alumni. "Stuyvesant needs to increase their numbers there. They're supposed to be the premier high school."

In the interview, Mr. Mamdani was quick to acknowledge the main reason he chose Bronx Science: "I couldn't get into Stuyvesant."

At the time, he was a student at the private Bank Street School for Children, near his family's home in the Morningside Heights neighborhood surrounding Columbia University, where his father had been a professor since they moved to New York when Mr. Mamdani was 7.

He was in many ways a typical city teen moving through some atypical circles with uncommon gumption.

Many Manhattan adolescents were made to socialize with their parents' friends. But few peers had parents like Mr. Mamdani's, attracting a procession of leading Palestinian American scholars to their apartment.

Many young trouble-seekers loved the stoner comedy "Harold & Kumar Go to White Castle." But only Mr. Mamdani was positioned to immediately recommend its co-star, Kal Penn, for a prestige drama directed by his mother, Mira Nair, an esteemed filmmaker. (Mr. Penn got the part and remains a friend. "I always love how comedy and satire can bring people together," he said in an email.)

Most days, Mr. Mamdani's chief interests included watching Arsenal soccer and playing the sport himself, dribbling a ball along the riverside fields of Manhattan or the overstuffed streets of Venice during a film-festival visit with Ms. Nair.

"Some of my closest friends, we were just united by soccer," Mr. Mamdani said of his early high school days on a 2016 podcast about Bronx Science hosted by Daniel Kisslinger, a close friend whom he met freshman year. ("'United by soccer,'" Mr. Mamdani repeated, self-critically. "It sounds like a yearbook quote they made up for me.")

Mr. Mamdani was one of the few nonwhite students commuting from Manhattan to the campus on West 205th Street, where roughly half the attendees generally come from Queens and 60 percent are immigrants or the children of immigrants, according to the alumni group.

For many, the daily journey was a solidarity-making schlep, coaxing commiseration at bleary hours. Administrators still cheerily appraise the extensive travel as a "feature of the Bronx Science experience" that burnishes the time-management skills and "resilience" of the school's charges.

Mr. Mamdani took the No. 1 train to a city bus, he said, often "banging on the door of the Bx10 that was crawling away." He and fellow travelers could find the Bronx Science slogan -- "We're Worth the Trip!" -- a little grating after nearly an hour in transit each way.

With some 700 students in his grade, Mr. Mamdani, wiry and baby-faced, still had a way of standing out.

"I wouldn't say that 14-year-olds have charisma," said Marc Kagan, his former history teacher, whose sister, Elena, was nominated to the Supreme Court during Mr. Mamdani's senior year. "But there are certain 14-year-olds who just kind of have something about them."

A self-proclaimed "disruptive personality," Mr. Mamdani goofed prolifically, once participating in an elaborate multiday, multiplayer competition in which students carried forks at all hours and faux-stabbed their adversaries, according to interviews and somehow-still-available Facebook posts from the time.

He kept playing soccer, helping to fulfill a team-wide pledge to consume inadvisable quantities of White Castle if the squad made the playoffs. "I was quite depressed immediately after eating," he said.

He saw concerts all over -- Lupe Fiasco, Common, Mos Def -- and explored the hipster highlands of Williamsburg, Brooklyn, recounting his disappointment when the resale retailer Buffalo Exchange offered only $10 (partially in store credit) for his unwanted clothes.

He regularly scoured a website chronicling "the top 10 free things to do in New York City," he said.

"He was the person who had the interest and the curiosity to try to understand outside of his bubble," Mr. Kisslinger said. "Some of that was about big things and important things. But some of that was just like, 'This is a big world out here, and let's go have some adventures.'"

Inside the classroom, peers described Mr. Mamdani as a good-not-great student who could seem more animated by other pursuits.

He has cited a song he wrote for a final project in a literature class, which "consisted of me rapping over 'Still D.R.E.' at 2 a.m."

"I think I got a B-plus," he said on a 2017 podcast.

At one early parent conference, Mr. Mamdani's father, Mahmood Mamdani, betrayed some concern.

"Zohran could be doing better than this," Mr. Kagan, the history teacher, remembered Professor Mamdani saying. "Zohran could be working harder."

Mr. Mamdani had a 95 in the class, Mr. Kagan recalled.

Mr. Kagan said he had told Professor Mamdani not to worry about the grade because "the wheels are spinning in your son's head."

Cricket Is Life

Mr. Mamdani did not strike his classmates as insecure. And he certainly did not seem to shy away from his identity, with his "Ugindia" hat and his habit of speaking Hindi in the halls.

Filling out a college application, he checked boxes indicating that he was both "Asian" and "Black or African American," straining to capture his background in bureaucratic binaries.

But beneath the surface, Mr. Mamdani has said, his days at Bronx Science were often "framed by whiteness," informing his anxieties and social choices.

"I remember wondering about my attractiveness to girls because I wasn't white," Mr. Mamdani said on the 2016 podcast. "There was still this feeling at Bronx Science that the cool kids were the white kids."

He was heartened, then, when local athletic bureaucracy conspired in his favor.

"It did seem cool," Mr. Kisslinger, his non-cricket friend, said of cricket's official debut.

Like many South Asian classmates, Mr. Mamdani had grown up watching the sport with relatives. Unlike many of them, he had spent much of his earlier Bronx Science life with mostly well-off white students, from what he later called his "Manhattan crew," who knew little of cricket.

Before long, Mr. Mamdani has said, he began socializing far more with the cricket guys, many of them lower-income students with family in places like India, Pakistan and Bangladesh.

He describes this period with almost reverential nostalgia, enumerating its lessons about his city, his roots, his theory of organizing, his recognition that he quite liked being the center of the action.

"I love being the bowler," he was quoted as saying in his senior yearbook, naming his preferred role in cricket, "because I feel like I have so much pull in how the game goes."

Many of his efforts are memorialized in Facebook posts, which found Mr. Mamdani practically begging teammates to attend practices and matches. "If you want to question people's commitment and things like that then lets start by showing up to games," he wrote to the group.

They would play at Ferry Point Park in the Bronx, scuffing up white uniforms with the school's wolverine mascot on the front, and on fields across Queens, where many of Mr. Mamdani's new friends lived.

Mr. Mamdani has credited his high school travels with immersing him in the borough that would become his home and political base, back when the most pressing question about his coalition was how many teammates would join him for postgame kebabs, with heaps of homework awaiting them.

At least once, Mr. Mamdani hosted a team dinner at his apartment, where the chasm in the players' family circumstances was unmistakable: One guest recalled being awed at the notion of a doorman building.

On campus, the cricketers became something of a fascination.

"It was just cool to kind of see brown culture thriving," said Josephine Ali, another classmate and friend, whose wedding to another Bronx Science alum Mr. Mamdani attended last year, alongside 15 other Bronx Science graduates.

The team's performance under Mr. Mamdani was mixed, though it did include a victory over Stuyvesant before his graduation in 2010.

Not so many years later, Mr. Mamdani's time at Bronx Science has echoed through a campaign that has dwelled on the prospect of generational change. (Mr. Cuomo, his chief rival, marked his own milestone the year that Mr. Mamdani graduated: his election as governor of New York, at the age of 52.)

Mr. Cuomo, who went to a Catholic high school in Queens, has attacked Mr. Mamdani's squishiness on the standardized high school exam "despite having personally benefited" from the system, and has proposed the addition of a new specialized high school in Queens.

The test remains popular with many Asian voters, a key bloc in Mr. Mamdani's Democratic primary win. More than half of the roughly 4,000 students who were admitted to the specialized schools this year were Asian American, according to city statistics.

Mr. Mamdani has said his reversal on abolishing the test reflected "the enormity of the task at hand" across the school system, gesturing vaguely at ambitions to "transform the conditions that then are the basis of that specialized high school test." (He has separately said he would end the city's gifted and talented program for kindergartners.)

Since the primary, Bronx Science text chains, alumni gatherings and Facebook groups have crackled with word of Mr. Mamdani's rise, dividing some graduates who cheer the institution's role in shaping him and others who cannot fathom that their alma mater produced someone so thoroughly left-wing.

Mr. Mamdani evinced school pride in a video last spring trolling The New York Post, which had written about his run for student government. ("Go Wolverines," he said, raising a fist, after feigning contrition for not conducting a "feasibility study" on his juice-for-all promise.)

And last January, while speaking at an event in Manhattan, Mr. Mamdani called out a surprise attendee he spotted sitting quietly in the crowd: Mr. Kagan.

Mr. Mamdani appeared older, the teacher allowed afterward, if not that much older.

"He doesn't actually look different," Mr. Kagan said. "But he had grown the beard."

Kitty Bennett and Alain Delaquérière contributed research.

The Origins of Zohran Mamdani's Long Game